The invention relates to a color cathode-ray tube, and, more particularly, to a system for suspending a color-selection frame/mask device arranged inside the glass bulb of a tube. The invention finds an application in any type of tube including support of a color-selection mask therein, and is more particularly suitable for tubes in which a mask is held under tension by a frame to which it is secured.
Conventional cathode-ray tubes include a color-selection mask situated at a precise distance from the inside of the glass front face of the tube, on which front face arrays of red, green and blue phosphors are deposited. Under the influence of three electron beams, each corresponding to a defined primary color, the arrays of phosphors allow images to be reproduced on the screen, the mask allowing each defined beam to illuminate only the phosphor of the corresponding color.
The color-selection mask should be arranged and held in a precise position within said tube, while the tube is operating. The holding functions are carried out by virtue of a generally very rigid rectangular metal frame to which the mask is conventionally welded. The frame/mask assembly is mounted in the front face of the tube by virtue of suspension means, including at least three metal pieces welded to the frame, each of said pieces including one end forming a spring and pierced with an aperture intended to engage one of the metal pins included in the glass front face. Two arrangements of the suspension means are conventionally used, either at the middle of the sides of the frame, or at the corners thereof.
The current trend is to produce tubes with increasingly flatter front faces, eventually evolving to become completely flat front faces. In order to produce tubes including such a front face, one technology consists in using a flat mask, held under tension in at least one direction. Such structures are described, for example, in U.S. Pat. 5,111,107 However, in order to maintain the flatness of the mask, a high tensile force has to be applied to it and the structure of the frame, which is required, and is heavy, using up a large amount of material. The present invention proposes to lighten the structure of the frame holding a mask under tension while reducing the number of metal pieces of the structure by using reinforcing pieces also acting as a means of support for the frame/mask system.
A color cathode-ray tube according to the present invention comprises a glass front face on which is deposited a screen of luminescent materials, a color-selection mask arranged close to the screen, and a frame to which the mask is fixed and which holds it under tension along at least one direction. The frame has a substantially rectangular shape defined by a pair of opposed long sides and a pair of likewise opposed short sides. At least two sides each include an edge in the form of a metal plate substantially parallel to the surface of the mask, the frame/mask assembly being held within the front face by support means interacting with pins fixed into the thickness of the front face. At least two support means each incorporate a metal piece including a first part extending over one of the surfaces of the plate. The first part is secured, for example by welding, to the plate. A second part extends in a direction substantially perpendicular to the surface of the mask.